Integrated magnet body and motor incorporating it

ABSTRACT

The integrated magnet body according to the invention is an integrated magnet body formed by laminating and securing a plurality of pieces of magnet through an insulating film between pieces of magnet, characterized in that the insulating film has a film thickness of 0.01 μm or more, and a ratio of a total sum of the thickness of the insulating films to an overall length in the laminating direction of the integrated magnet body is in a range of from 0.0005 to 3%. The integrated magnet body according to the invention is excellent in insulating property and effective volume ratio and thus can attain high efficiency of a motor by installing the integrated magnet body in the motor.

TECHNICAL FIELD

The present invention relates to an integrated magnet body used in amotor for an electric vehicle and a motor for a home electric appliance,and a motor incorporating the same. More specifically, it relates to anintegrated magnet body excellent in insulating property and effectivevolume ratio, and a high efficiency motor incorporating the same.

BACKGROUND ART

As a motor for an electric vehicle (such as EV: electric vehicle andHEV: hybrid electric vehicle) and a motor for a home electric appliance,for example, brushless motors, such as so-called IPM (interior permanentmagnet motor) and SPM (surface permanent magnet motor), have beendeveloped, which uses a rare earth metal-based permanent magnetrepresented by an R—Fe—B based permanent magnet embedded in a rotorformed with silicon steel plates or the like.

In recent years, improvements in materials for rare earth metal-basedpermanent magnet proceed, and performances of motors are also improvedaccording thereto. However, because the rare earth metal-based permanentmagnet has electroconductivity, it has problems where such disadvantagesare caused upon application of an alternating current magnetic field onthe magnet, in that an eddy current is generated in the magnet to lowerthe efficiency of the motor as an eddy current loss, the characteristicsof the motor are deteriorated by heat demagnetization of the magnet.

As a method for lowering the eddy current occurring in the magnet, thereis such a method in that the magnet is divided, and plural magnet piecesare laminated with electric insulation therebetween to form anintegrated magnet body (see, for example, JP-A-4-79741). Conventionally,upon employing the method, for example, an adhesive having insulatingproperty is coated on the magnet pieces, and one of the magnet pieces isadhered and fixed with another.

However, in the method where an adhesive having insulating property iscoated on the surface of the magnet pieces, followed by adhering andfixing, it is necessary that the film thickness of the adhesive formedbetween the magnetic piece and another magnetic piece is as thick as 100μm or more to assure the prescribed adhesion strength. Therefore, in anintegrated magnet body having the prescribed dimension, even whensufficient insulating property can be obtained among the respectivemagnet pieces, the volume ratio of the magnet pieces themselvesconstituting the integrated magnet body (hereinafter referred to as aneffective volume ratio) is lowered corresponding to the thickness of theadhesive. As a result, the effective magnetic flux density is lowered tocause deterioration of the characteristics of the motor, which bringsabout deterioration of the efficiency of the motor. Furthermore, in thismethod, the thickness of the adhesive influences the dimensionalaccuracy, and thus an integrated magnet body having high dimensionalaccuracy cannot be obtained.

Accordingly, an object of the invention is to provide an integratedmagnet body excellent in insulating property and effective volume ratio,and a high efficiency motor having the same installed therein.

DISCLOSURE OF THE INVENTION

As a result of various investigations made by the inventors in view ofthe foregoing standpoints, it has been found that a film havingexcellent insulating property only with a thin film is formed betweenone magnet piece and another magnet piece, and the film thickness of theinsulating film and the ratio of the total sum of the thickness of theinsulating films to the overall length in the laminating direction ofthe integrated magnet body are set at particular values, whereby anintegrated magnet body excellent in insulating property and effectivevolume ratio can be obtained, and an efficiency of a motor can beimproved by installing the integrated magnet body in the motor.

The invention has been made based on the foregoing findings, and theintegrated magnet body of the invention is, as described in the claim 1,an integrated magnet body formed by laminating and securing a pluralityof pieces of magnet through an insulating film between pieces of magnet,characterized in that the insulating film has a film thickness of 0.01μm or more, and a ratio (l/L) of a total sum of the thickness of theinsulating films (l) to an overall length in the laminating direction ofthe integrated magnet body (L) is in a range of from 0.0005 to 3%.

The integrated magnet body as described in the claim 2 is an integratedmagnet body as described in the claim 1, characterized in that the filmthickness of the insulating film is 50 μm or less.

The integrated magnet body as described in the claim 3 is an integratedmagnet body as described in the claim 1 or 2, characterized in that theratio (l/L) of the total sum of the thickness of the insulating films(l) to the overall length in the laminating direction of the integratedmagnet body (L) is in a range of from 0.01 to 1%.

The integrated magnet body as described in the claim 4 is an integratedmagnet body as described in one of the claims 1 to 3, characterized inthat the insulating film is an inorganic insulating film containing, asa main component, at least one selected from a chromium oxide, aphosphorous oxide, a silicon oxide, an aluminum oxide, a titanium oxideand a zirconium oxide.

The integrated magnet body as described in the claim 5 is an integratedmagnet body as described in one of the claims 1 to 3, characterized inthat the insulating film is an organic insulating film containing athermoplastic resin and/or a thermosetting resin.

The integrated magnet body as described in the claim 6 is an integratedmagnet body as described in one of the claims 1 to 5, characterized inthat the integrated magnet body is formed by securing by encompassingand integrating, with an organic resin, a laminated body obtained bylaminating a plurality of pieces of magnet through an insulating filmbetween the pieces of magnet.

The integrated magnet body as described in the claim 7 is an integratedmagnet body as described in one of the claims 1 to 5, characterized inthat the integrated magnet body is formed by securing by binding, with ahigh strength fiber strip, a laminated body obtained by laminating aplurality of pieces of magnet through an insulating film between thepieces of magnet.

The integrated magnet body as described in the claim 8 is an integratedmagnet body as described in one of the claims 1 to 7, characterized inthat the pieces of magnet are a rare earth metal-based permanent magnet.

The motor of the invention is, as described in the claim 9,characterized by comprising an integrated magnet body as described inone of the claims 1 to 8 installed therein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a reference view for calculating the ratio of the total sum ofthe thickness of the insulating films between the pieces of magnet tothe overall length in the laminating direction of the integrated magnetbody.

FIG. 2 is a perspective explanatory view showing an example of asecuring method for obtaining an integrated magnet body according to theinvention.

FIG. 3 is a perspective view showing an example of an integrated magnetbody according to the invention.

FIG. 4 is an explanatory view showing a constitutional example of anIPM.

BEST MODE FOR CARRYING OUT THE INVENTION

The integrated magnet body of the invention is an integrated magnet bodyformed by laminating and securing a plurality of pieces of magnetthrough an insulating film between pieces of magnet, characterized inthat the insulating film has a film thickness of 0.01 μm or more, and aratio (l/L) of a total sum of the thickness of the insulating films (l)to an overall length in the laminating direction of the integratedmagnet body (L) is in a range of from 0.0005 to 3%.

The method for making the insulating film intervening the pieces ofmagnet may be such an embodiment that the insulating film is formed onone contact surface of the pieces of magnet in contact with each other,and the adjacent piece of magnet is laminated on the insulating filmthus formed, or such an embodiment that the insulating films are formedon both contact surfaces of both the pieces of magnet, and theinsulating films thus formed are made in contact with each other toaccomplish lamination. It is not essential that the insulating film isformed only between the pieces of magnet, and therefore, the insulatingfilm may be formed on other surfaces than the contact surfaces of thepieces of magnet depending on necessity in the foregoing embodiments. Inparticular, the later embodiment among the embodiments can generally beattained by forming the insulating films on the whole surfaces of therespective pieces of magnet.

Examples of the insulating film applied in the invention include aninorganic insulating film containing, as a main component, at least oneselected from a chromium oxide, a phosphorous oxide, a silicon oxide, analuminum oxide, a titanium oxide and a zirconium oxide. Because atreating liquid for forming the films has good wettability, the treatingliquid quickly penetrates on the surface of the pieces of magnet, andtherefore, such a film can be formed that is dense and excellent inadhesion and is excellent in insulating property only with a thin film.

Examples of the method for forming an insulating film containing achromium oxide as a main component on the surface of the piece of magnetinclude such a method that a treating liquid containing at least onekind selected from chromic anhydride and a bichromate is coated on thesurface of the piece of magnet, and then it is subjected to a heattreatment. Examples of the bichromate include sodium bichromate,potassium bichromate and the like.

The chromium oxide may be, for example, a composite chromium oxide ofchromium and a divalent metal (such as Mg, Ca, Zr, Sr, Ba, Ni, Co, Zn,Mn, Sn, Pb, Cu, and the like). An insulating film containing thecomposite chromium oxide as a main component, particularly an insulatingfilm containing the composite chromium oxide of chromium and Mg, Ca, Zr,Zn, Mn and the like, is such a film that is uniform and dense and isexcellent in adhesion in comparison to the foregoing insulating films,and it is excellent in insulating property only with a thin film. Theinsulating film can be formed on the surface of the piece of magnet, forexample, by using a treating liquid formed in such a manner that anoxide, a hydroxide, a carbonate or the like of a divalent metal is addedto the treating liquid containing at least one kind selected fromchromic anhydride and a bichromate, and furthermore, a polyhydricalcohol, such as ethylene glycol and the like, is added as a reducingagent suitably.

In order to improve the heat resistance and the corrosion resistance ofthe insulating film, boric acid, phosphoric acid and the like may beappropriately added to the treating liquid.

An insulating film containing an organic resin may be formed by using atreating liquid formed by adding an emulsion type organic resin or awater soluble organic resin to the aforementioned treating liquid. Whenthe film is formed by using the treating liquid having an organic resinadded thereto, improvement of the adhesion property of the film to thepiece of magnet, prevention of cracking of the film upon forming thefilm, improvement of the heat resistance of the film, improvement of theadhesion property of the film to the adhesive, improvement of thewettability between the treating liquid and the surface of the piece ofmagnet, and the like can be attained. Examples of the organic resininclude an acrylic resin, a urethane resin, a vinyl acetate resin, anepoxy resin and a copolymerization product of these organic resins. Theorganic resin may be those having been subjected to various kinds ofmodification treatments. The addition of a urethane-modified acrylicresin is effective for improvement of the heat resistance of the film.The addition of an acrylic-modified epoxy resin or a silica-modifiedacrylic resin is effective for improvement of the adhesion property ofthe film to the adhesive.

Examples of the method for forming an insulating film containing aphosphorous oxide as a main component on the surface of the piece ofmagnet include such a method that a treating liquid containing ahypophosphite, such as sodium hypophosphite and the like, and anoxidizing agent, such as sodium nitrate and the like, or a treatingliquid containing a phosphate, such as iron phosphate, calciumphosphate, zinc phosphate and the like, is coated on the surface of thepiece of magnet, and then it is subjected to a heat treatment. There aresome cases where a hypophosphite and a phosphate are present in theinsulating film.

Examples of the method for forming an insulating film containing asilicon oxide as a main component on the surface of the piece of magnetinclude such a method that a treating liquid containing a silicate, suchas sodium silicate and the like, and a hydroxide is coated on thesurface of the piece of magnet, and then it is subjected to a heattreatment. Further examples thereof include such a method that the filmis formed by a coating and thermal decomposition method using a treatingliquid containing a silicon compound, such as tetraethoxysilane and thelike. Still further examples thereof include such a method that the filmis formed by a sol-gel film forming method using a treating liquidobtained by a hydrolysis reaction, a polymerization reaction and thelike of a silicon compound, and the like method.

Similarly, examples of the method for forming an insulating filmcontaining an aluminum oxide as a main component on the surface of thepiece of magnet include a method of forming by using a treating liquidcontaining an aluminate, such as potassium aluminate and the like, and ahydroxide, a method of forming by a coating and thermal decompositionmethod using a treating liquid containing an aluminum compound, such asaluminum acetylacetnate and the like, a method of forming by a sol-gelfilm forming method using a treating liquid obtained by a hydrolysisreaction, a polymerization reaction and the like of an aluminumcompound, and the like method.

Similarly, examples of the method for forming an insulating filmcontaining a titanium oxide as a main component on the surface of thepiece of magnet include a method of forming by using a treating liquidcontaining a titanate, such as sodium titanate and the like, and ahydroxide, a method of forming by a coating and thermal decompositionmethod using a treating liquid containing a titanium compound, such as atitanium carboxylate and the like, a method of forming by a sol-gel filmforming method using a treating liquid obtained by a hydrolysisreaction, a polymerization reaction and the like of a titanium compound,and the like method.

The insulating film may be those containing a composite metallic oxidecontaining both a silicon oxide and an aluminum oxide, as a maincomponent. The film may be formed, for example, by using a treatingliquid containing a silicon compound and an aluminum compound. Aninsulating film containing a zirconium oxide as a main component can beformed on the surface of the piece of magnet similarly to the insulatingfilms containing a silicon oxide, an aluminum oxide or a titanium oxideas a main component.

Examples of the insulating film applied to the invention include anorganic insulating film formed with a thermoplastic resin and/or athermosetting resin, in addition to the foregoing inorganic insulatingfilms. Examples of the method for forming the organic insulating film onthe surface of the piece of magnet include such a method that a treatingliquid containing the resin is coated on the surface of the piece ofmagnet, and then it is subjected to a heat treatment.

As the thermoplastic resin, a fluorine resin, saturated polyester,polyvinyl alcohol, polyvinyl acetal and the like can be used in additionto the acrylic resin, the urethane resin and the vinyl acetate resindescribed in the foregoing. These resins may be those having beensubjected to various kinds of modification treatments, and maybe thosehaving been emulsified. These resins may also be used solely or may beused after mixing an appropriate combination thereof.

As the thermosetting resin, a phenol resin, a melamine resin,unsaturated polyester, a silicone resin, polyurethane, an alkyd resin, apolyimide resin and the like can be used in addition to the epoxy resindescribed in the foregoing. These resins may be those having beensubjected to various kinds of modification treatments, and maybe thosehaving been emulsified. These resins may also be used solely or may beused after mixing an appropriate combination thereof.

Before forming the organic insulating film on the surface of the pieceof magnet, various kinds of primer treatments may be carried out inorder to improve the adhesion property between the piece of magnet andthe film and to prevent deterioration of insulating property due toprogress of corrosion of the piece of magnet. Examples of the primertreatment include an alkali treatment by coating an alkali solution of0.01 to 0.1 N (such as an aqueous solution of lithium hydroxide, sodiumhydroxide, potassium hydroxide, sodium carbonate or the like, aqueousammonia and the like) on the surface of the piece of magnet, followed byheating, an alkali silicate treatment by coating a solution containinglithium silicate, sodium silicate and the like on the surface of thepiece of magnet, followed by heating, as described in JP-A-9-7867 andthe like, a molybdic acid treatment by coating a solution containingmolybdic acid or a salt thereof on the surface of the piece of magnet,followed by heating, an oxidation treatment by heating the piece ofmagnet in an inert gas at 400 to 700° C., and the like method.

As a method for coating the treating liquid on the surface of the pieceof magnet, for example, a dipping method, a dipping and spinning method,spray coating, and roller coating are employed. The surface of the pieceof magnet before coating the treating liquid may be subjected to apre-treatment, such as degreasing by using an organic solvent, washingwith a weak acid by using an aqueous solution of phosphoric acid, aceticacid, oxalic acid, nitric acid or the like, for removing a surfacemodification layer, which maybe formed on the production process (suchas a working step and a polishing step), and the like.

The thickness of the insulating film formed between the pieces of magnetis 0.01 μm or more. When the film thickness is less than 0.01 μm, thereis a possibility that it influences the insulating property and thecorrosion resistance of the film. When the thickness of the insulatingfilm is too large, on the other hand, the effective volume ratio of theintegrated magnet body is lowered corresponding to the thickness, so asto lower the effective magnetic flux density, whereby the motorefficiency is lowered. Therefore, the film thickness is preferably 50 μmor less, more preferably 20 μm or less, and further preferably 10 μm orless.

The ratio (l/L) of the total sum of the thickness of the insulatingfilms intervening the pieces of magnet (l) to the overall length in thelaminating direction of the integrated magnet body (L) is in a range offrom 0.0005 to 3%. The calculation method for the ratio will bedescribed with reference to FIG. 1.

In such an embodiment as shown in (a) that an insulating film is formedon one of the contact surfaces of the pieces of magnet in contact witheach other, and then the adjacent piece of magnet is laminated on theinsulating film thus formed, as the method for making the insulatingfilm intervening the pieces of magnet (for example, as the relationshipbetween the piece of magnet m₁ and the piece of magnet m₂ is explained,the insulating property between the piece of magnet m₁ and the piece ofmagnet m₂ is assured only with the insulating film f₁ formed on thecontact surface of the piece of magnet m₁ in contact with the piece ofmagnet m₂. With respect to the relationship between the piece of magnetm₃ and the piece of magnet m₄, the insulating property between the pieceof magnet m₃ and the piece of magnet m₄ is assured only with theinsulating film f₃ formed on the contact surface of the piece of magnetm₃ in contact with the piece of magnet m₄, and no insulating film isformed on the piece of magnet m₄), the overall length in the laminatingdirection of the integrated magnet body is defined by L, and the totalsum of the thickness of the insulating films intervening the pieces ofmagnet l is defined by (l₁+l₂+l₃).

In such an embodiment as shown in (b) that an insulating films areformed on both contact surfaces of both the pieces of magnet, andlamination is carried out by contacting the respective insulating filmsthus formed, the overall length in the laminating direction of theintegrated magnet body is defined by L, and the total sum of thethickness of the insulating films intervening the pieces of magnet l isdefined by (l₁₊₂+l₂₊₃+l₃₊₄).

It is not essential that the insulating film is formed only between thepieces of magnet as described in the foregoing, it is possible that thefilm may be formed on the whole surface of the respective pieces ofmagnet as shown in (b) of FIG. 1. In this case, the thickness of theinsulating films on both ends is not included in the overall length inthe laminating direction of the integrated magnet body. Since theinsulating film applied in the invention is a thin film, even when thefilm is formed on the whole surface of the pieces of magnet, it does notseverely influence the effective volume ratio of the integrated magnetbody. From the standpoint of assuring corrosion resistance of the piecesof magnet, it is preferred that the insulating film is formed on thewhole surface of the pieces of magnet to a thickness of 0.005 μm ormore.

In the case where an electroconductive film, such as an aluminum film,is formed on the surfaces of the respective pieces of magnet in order toimpart corrosion resistance thereto, and then the insulating film of theinvention is formed thereon, the calculation is carried out by assumingthat the thickness of the electroconductive film is part of the lengthof the pieces of magnet.

In the case where the ratio (l/L) of the total sum of the thickness ofthe insulating films (l) to the overall length in the laminatingdirection of the integrated magnet body (L) is less than 0.0005%, thereare some cases where the insulating property is insufficient to causeheat generation upon driving the motor, whereby the motor efficiency islowered. When the ratio exceeds 3%, on the other hand, there are somecases where the effective volume ratio of the integrated magnet body islowered to lower the effective magnetic flux density, whereby the motorefficiency is lowered. The ratio is preferably in a range of from 0.01to 1% from a practical standpoint.

Examples of the method for laminating and securing a plurality of piecesof magnet to form an integrated magnet body include such a method that,as shown in FIG. 2, an outer frame 3 formed with an organic resin, suchas unsaturated polyester, an epoxy resin and the like, is previouslyprepared, and a laminated body obtained by laminating a plurality ofpieces of magnet 1 through an insulating film between the pieces ofmagnet is incorporated therein, followed by securing by encompassing andintegrating through application of pressure and heat from the exterior,so as to make the integrated magnet body.

Examples thereof also include such a method that a laminated bodyobtained by laminating a plurality of pieces of magnet through aninsulating film between the pieces of magnet is secured by binding witha high strength fiber strip to make the integrated magnet body. Examplesof the high strength fiber strip include aramid fibers (aromaticpolyamide fibers). Examples of the specific method for binding with ahigh strength fiber strip include such a method that, as shown in FIG.3, a woven fabric in a tape form of aramid fibers 4, in whichoverlapping parts at the ends thereof have been impregnated with anepoxy resin or the like to form joint parts 4 a, is wound on thelaminated body, and then the joint parts 4 a are thermally fused toobtain the integrated magnet body 2. In the integrated magnet body shownin FIG. 3, because magnetic poles are formed on the principal surfaces(the upper and lower surfaces in the figure) of the laminated body, itis not effective that the high strength fiber strip is arranged on theprincipal surfaces from the standpoint of magnetic efficiency.Therefore, the high strength fiber strip is arranged on the sidesurfaces of the laminated body.

Furthermore, it is also possible that the whole laminated body issecured by coating the whole surface thereof with a thermosetting resinor the like using the known injection molding technique to form theintegrated magnet body.

Various kinds of organic resins can be selected to obtain the organicinsulating film as described in the foregoing, and a thermoplastic resinsuch as an acrylic resin, a mixed resin of that resin and athermosetting resin such as an epoxy resin, and a resin formed bysubjecting these resins to a modification treatment have thermal fusingproperty. Therefore, for example, the integrated magnet body can beefficiently obtained in such a manner that an insulating film is formedon the whole surface of the pieces of magnet by using the resin, and thepieces of magnet are then laminated through the insulating films,followed by thermal fusing the insulating films under a light pressurewith heating the laminated body to a prescribed temperature.

Examples of the pieces of magnet applied in the invention include aknown rare earth metal-based permanent magnet, such as an R—Co basedpermanent magnet, an R—Fe—B based permanent magnet, an R—Fe—N basedpermanent magnet and the like. Among these, an R—Fe—B based permanentmagnet is preferred from the standpoint of high magneticcharacteristics, excellent mass-productivity and economy, and the like.The rare earth element (R) in the rare earth metal-based permanentmagnet preferably contains at least one kind of Nd, Pr, Dy, Ho, Tb andSm, or further contains at least one kind of La, Ce, Gd, Er, Eu, Tm, Yb,Lu and Y.

While only one kind of R is generally sufficient, a mixture of two ormore kinds thereof (misch metal, didymium and the like) may bepractically used due to reasons of convenience in availability.

Furthermore, improvement of the coercive force and the rectangularity ofa demagnetizing curve, improvement of the productivity, and low cost canbe attained by adding at least one kind of Al, Ti, V, Cr, Mn, Bi, Nb,Ta, Mo, W, Sb, Ge, Sn, Zr, Ni, Si, Zn, Hf and Ga.

The integrated magnet body of the invention obtained in the foregoingmanner is, for example, installed in an IPM by the method shown in FIG.4. That is, the IPM 5 is constituted with a core 6 and a rotor 7arranged thereinside, and the integrated magnet bodies 9 of theinvention are embedded as rotor magnets 8 in six sites in the rotor 7.The motor thus obtained is a motor having high efficiency owing to theintegrated magnet body excellent in insulating property and effectivevolume ratio.

EXAMPLE

The invention will be described in more detail with reference toexamples. While the following examples use sintered magnets, theinvention can also be applied to a bond magnet as well as the sinteredmagnet.

Example A (Examples 1 to 5)

The following experiment was carried out by using an Nd—Fe—B basedpermanent magnet (sintered magnet) having a composition of 26 wt % ofNd, 72 wt % of Fe, 1 wt % of B and 1 wt % of Co having a dimension of 10mm in length, 50 mm in width and 5 mm in height as pieces of magnet.

The pieces of magnet were degreased with an organic solvent and thenwashed with a weak acid using a 5 wt % phosphoric acid aqueous solution.A treating liquid stock solution was prepared, which contained 350 g/lof chromic acid, 70 g/l of magnesium hydroxide, 50 g/l (in terms ofresin content) of an acrylic resin emulsion (Polytlon F2000, produced byAsahi Kasei Corp.), 5 g/l of ethylene glycol as a reducing agent and 20g/l of boric acid. Treating liquids having various concentrations wereprepared by diluting the treating liquid stock solution with water, andthe treating liquid was coated on the whole surfaces of the respectivepieces of magnet by the dipping method and subjected to a heat treatmentat 280° C. for 20 minutes, whereby insulating films containing acomposite chromium oxide of chromium and magnesium as a main componenthaving various values of thickness were formed on the whole surfaces ofthe pieces of magnet. The results of the measurement of thickness areshown in Table 1. The pieces of magnet were allowed to stand under hightemperature and high humidity conditions of a temperature of 80° C. anda relative humidity of 90% for 300 hours to carry out a corrosionresistance test. The results are shown in Table 1.

Eight pieces of the pieces of magnet having the insulating film on thewhole surface thereof were laminated in the height direction in an outerframe having been produced by molding unsaturated polyester, and weresecured through encompassing and integrating by applying pressure andheat from the exterior, whereby an integrated magnet body was obtained(see FIG. 2). The integrated magnet body was installed in an IPM(four-pole, 15 kW, pulse width modulation type), and the motorefficiency (output electric power/input electric power) was evaluated ata rotation number of 5,400 rpm. The results are shown in Table 1.

Comparative Example 1

The pieces of magnet described in Example A were used, and an insulatingfilm containing a composite chromium oxide of chromium and magnesium asa main component having a thickness of 0.004 μm was formed on the wholesurfaces of the pieces of magnet in the same manner as in Example A. Thepieces of magnet having the insulating film on the whole surface thereofwere subjected to the corrosion resistance test described in Example A.The result is shown in Table 1. An integrated magnet body was producedby using the pieces of magnet having the insulating film on the wholesurface thereof in the same manner as in Example A, and the motorefficiency was evaluated. The result is shown in Table 1.

Comparative Example 2

Pieces of magnet that were the same as the pieces of magnet used inExample A except that the height was 4.85 mm to obtain the overalllength (L) of the integrated magnet body that is substantially the sameas in Example A was used, and an insulating film containing a compositechromium oxide of chromium and magnesium as a main component having athickness of 100 μm was formed on the whole surfaces of the pieces ofmagnet in the same manner as in Example A. The pieces of magnet havingthe insulating film on the whole surface thereof were subjected to thecorrosion resistance test described in Example A. The result is shown inTable 1. An integrated magnet body was produced by using the pieces ofmagnet having the insulating film on the whole surface thereof in thesame manner as in Example A, and the motor efficiency was evaluated. Theresult is shown in Table 1.

TABLE 1 Thickness of insulating film formed on Result Motor respectivepieces of corrosion efficiency of magnet (μm) resistance test l/L (%)(%) Comparative 0.004 partially 0.00014 82 Example 1 rust formed Example1 0.05 no rust formed 0.0018  93 Example 2 0.5 no rust formed 0.018  92Example 3 2.5 no rust formed 0.088  90 Example 4 5 no rust formed 0.18  89 Example 5 10 no rust formed 0.35   89 Comparative 100 no rust formed3.5   85 Example 2

As apparent from Table 1, the integrated magnet bodies of Example A(Examples 1 to 5) exhibited excellent insulating property, therespective pieces of magnet thereof exhibited excellent corrosionresistance, and the IPM having them installed therein exhibited a motorefficiency of about 90% or more. The integrated magnet body ofComparative Example 1 had the insulating film that did not have athickness exerting sufficient insulating property, and therefore, theIPM having the same installed therein exhibited a poor motor efficiency.The respective pieces of magnet thereof exhibited poor corrosionresistance. The integrated magnet body of Comparative Example 2 had theinsulating film having a large thickness to lower the effective volumeratio of the integrated magnet body corresponding to the extent of thethickness, and therefore, the IPM having the same installed thereinexhibited a poor motor efficiency.

Example B (Examples 6 to 11)

The following experiment was carried out by using the same pieces ofmagnet as the pieces of magnet described in Example A. An insulatingfilm having a thickness of 5 μm was formed on the whole surface of thepieces of magnet by using the treating liquids shown in Table 2 in thesame manner as in Example A. The pieces of magnet having the insulatingfilm on the whole surface thereof were subjected to the corrosionresistance test described in Example A. The results are shown in Table3.

A laminated body obtained by laminating eight pieces of the pieces ofmagnet having the insulating film on the whole surface thereof in theheight direction was secured by binding with a high strength fiber stripformed with aramid fibers as shown in FIG. 3 to obtain an integratedmagnet body (l/L: 0.18%). The integrated magnet body was evaluated formotor efficiency under the same conditions as in Example A. The resultsare shown in Table 3.

TABLE 2 Main component Treating liquid components of insulating filmExample 6 sodium hypophosphite, sodium phosphorous oxide nitrate(oxidizing agent) Example 7 tetraethoxysilane (15 wt % in terms siliconoxide of SiO₂), ethanol, hydrochloric acid, ammonia Example 8 potassiumaluminate, zirconium aluminum oxide hydroxide Example 9 aluminumacetylacetnate (10 wt % in aluminum oxide terms of Al₂O₃), isopropylalcohol, acetic acid Example 10 sodium titanate, calcium hydroxidetitanium oxide Example 11 titanium carboxylate (15 wt % in titaniumoxide terms of TiO₂), aminoalcohol, ammonia

TABLE 3 Result of corrosion resistance test Motor efficiency (%) Example6 no rust formed 91 Example 7 no rust formed 90 Example 8 no rust formed91 Example 9 no rust formed 92 Example 10 no rust formed 90 Example 11no rust formed 92

As apparent from Table 3, the integrated magnet bodies of Example B(Examples 6 to 11) exhibited excellent insulating property, therespective pieces of magnet thereof exhibited excellent corrosionresistance, and the IPM having them installed therein exhibited a highmotor efficiency of 90% or more.

Example C (Examples 12 and 13)

The following experiment was carried out by using an Nd—Fe—B basedpermanent magnet (sintered magnet) having a composition of 23 wt % ofNd, 75 wt % of Fe, 1 wt % of B and 1 wt % of Co having a dimension of 10mm in length, 50 mm in width and 5 mm in height as pieces of magnet.

The pieces of magnet were degreased with an organic solvent and thenwashed with a weak acid using a 5 wt % phosphoric acid aqueous solution.A treating liquid stock solution was prepared by mixing an acrylic resinemulsion (Polytlon F2000, produced by Asahi Kasei Corp.), an epoxy resin(YUKA-RESINE-201, produced by Yoshimura Oil Chemical Co., Ltd.) and anamine based epoxy resin curing agent (YUKA-RESIN H-35, produced byYoshimura Oil Chemical Co., Ltd.) as resin components in a weight ratioof 50/42/8. Treating liquids having two kinds of concentrations wereprepared by diluting the treating liquid stock solution with water, andthe treating liquid was coated on the whole surfaces of the respectivepieces of magnet by the dipping method and subjected to a heat treatmentat 120° C. for 10 minutes, whereby organic insulating films having athickness of 2.5 μm or 6 μm were formed on the whole surfaces of thepieces of magnet. The pieces of magnet having the insulating film on thewhole surface thereof were subjected to the corrosion resistance testdescribed in Example A. The results are shown in Table 4.

Eight pieces of the pieces of magnet having the insulating film on thewhole surface thereof were laminated in the height direction, and theresulting laminated body was secured by thermal fusing the insulatingfilms under heating to 250° C. with light pressure to obtain anintegrated magnet body. The integrated magnet body was installed in anIPM (eight-pole, 10 kW, pulse width modulation type), and the motorefficiency (output electric power/input electric power) was evaluated ata rotation number of 7,000 rpm. The results are shown in Table 4.

Comparative Example 3

Pieces of magnet that were the same as the pieces of magnet used inExample C except that the height was 4.85 mm to obtain the overalllength (L) of the integrated magnet body that is substantially the sameas in Example C was used, and an organic insulating film having athickness of 100 μm was formed on the whole surfaces of the pieces ofmagnet in the same manner as in Example C. The pieces of magnet havingthe insulating film on the whole surface thereof were subjected to thecorrosion resistance test described in Example A. The result is shown inTable 4. An integrated magnet body was produced by using the pieces ofmagnet having the insulating film on the whole surface thereof in thesame manner as in Example C, and the motor efficiency was evaluated. Theresult is shown in Table 4.

TABLE 4 Thickness of insulating film formed on Result Motor respectivepieces of corrosion efficiency of magnet (μm) resistance test l/L (%)(%) Example 12 2.5 no rust formed 0.088 91 Example 13 6 no rust formed0.21  88 Comparative 100 no rust formed 3.5  82 Example 3

As apparent from Table 4, the integrated magnet bodies of Example C(Examples 12 and 13) exhibited excellent insulating property, therespective pieces of magnet thereof exhibited excellent corrosionresistance, and the IPM having them installed therein exhibited a motorefficiency of about 90%. The integrated magnet body of ComparativeExample 3 had the insulating film having a large thickness to lower theeffective volume ratio of the integrated magnet body corresponding tothe extent of the thickness, and therefore, the IPM having the sameinstalled therein exhibited a poor motor efficiency.

Example D (Examples 14 to 15)

The following experiment was carried out by using the same pieces ofmagnet as the pieces of magnet described in Example C. A treating liquidstock solution was prepared by mixing an acrylic-modified epoxy resin(YUKA-RESIN KE-516, produced by Yoshimura Oil Chemical Co., Ltd.) and anamine based epoxy resin curing agent (YUKA-RESINH-35, produced byYoshimura Oil Chemical Co., Ltd.) as resin components in a weight ratioof 90/10. Treating liquids having two kinds of concentrations wereprepared by diluting the treating liquid stock solution with water, andthe treating liquid was coated on the whole surfaces of the respectivepieces of magnet by the dipping method and subjected to a heat treatmentat 150° C. for 10 minutes, whereby organic insulating films having athickness of 1 μm or 6 μm were formed on the whole surfaces of thepieces of magnet. The pieces of magnet having the insulating film on thewhole surface thereof were subjected to the corrosion resistance testdescribed in Example A. The results are shown in Table 5. An integratedmagnet body was produced by using the pieces of magnet having theinsulating film on the whole surface thereof in the same manner as inExample C, and the motor efficiency was evaluated. The results are shownin Table 5.

TABLE 5 Thickness of insulating film formed on Result Motor respectivepieces of corrosion efficiency of magnet (μm) resistance test l/L (%)(%) Example 14 1 no rust formed 0.035 93 Example 15 6 no rust formed0.21  91

As apparent from Table 5, the integrated magnet bodies of Example D(Examples 14 and 15) exhibited excellent insulating property, therespective pieces of magnet thereof exhibited excellent corrosionresistance, and the IPM having them installed therein exhibited a motorefficiency of 90% or more.

Example E (Examples 16 to 18)

An Nd—Fe—B based permanent magnet (sintered magnet) having a compositionof 26 wt % of Nd, 72 wt % of Fe, 1 wt % of B and 1 wt % of Co having adimension of 10 mm in length, 30 mm in width and 3 mm in height was usedas pieces of magnet and was subjected to the following experiment afterbeing degreased with an organic solvent and then washed with a weak acidusing a 5 wt % nitric acid aqueous solution.

The following experiment was carried out for Example 16. The pieces ofmagnet having been washed with a weak acid were dipped in a 0.1 N sodiumhydroxide aqueous solution at 50° C. for 20 seconds as a primertreatment, and after flashing the solution by air blowing, it wassubjected to a heat treatment at 120° C. for 10 minutes. The wholesurface of the pieces of magnet having been subjected to the primertreatment was coated with a treating liquid prepared by mixing anaqueous urethane resin emulsion (UCOAT UWS-145, produced by SanyoChemical Industries, Ltd.) and a melamine crosslinking agent (Cymel 325,produced by Mitsui Cytec, Ltd.) as resin components in a weight ratio of85/15 and diluting with water by the dipping method, and it wassubjected to a heat treatment at 150° C. for 20 minutes to form anorganic insulating film having a thickness of 7 μm on the whole surfaceof the pieces of magnet. The pieces of magnet having the insulating filmon the whole surface thereof were subjected to the corrosion resistancetest described in Example A, and no formation of rust was observed. Anintegrated magnet body (l/L: 0.41%) was produced by using the pieces ofmagnet having the insulating film on the whole surface thereof in thesame manner as in Example A and evaluated for motor efficiency, and anIPM having the integrated magnet body installed therein exhibited amotor efficiency of 90%.

The following experiment was carried out for Example 17. The pieces ofmagnet having been washed with a weak acid were dipped in a treatingliquid containing 0.1 mol/L of sodium molybdate, 0.18 mol/L ofphosphoric acid and 0.1 mol/L of sodium nitrate for 15 minutes as aprimer treatment, and after washing with water, it was subjected to aheat treatment at 150° C. for 5 minutes. The whole surface of the piecesof magnet having been subjected to the primer treatment was spray-coatedwith a treating liquid containing 55% by weight (in terms of resincontent) of an aqueous urethane-modified epoxy resin (YUKA-RESIN KE-163,produced by Yoshimura Oil Chemical Co., Ltd.), and it was subjected to aheat treatment at 180° C. for 20 minutes to form an organic insulatingfilm having a thickness of 15 μm on the whole surface of the pieces ofmagnet. The pieces of magnet having the insulating film on the wholesurface thereof were subjected to the corrosion resistance testdescribed in Example A, and no formation of rust was observed. Anintegrated magnet body (l/L: 0.87%) was produced by using the pieces ofmagnet having the insulating film on the whole surface thereof in thesame manner as in Example A and evaluated for motor efficiency, and anIPM having the integrated magnet body installed therein exhibited amotor efficiency of 88%.

The following experiment was carried out for Example 18. The pieces ofmagnet having been washed with a weak acid were subjected to a heattreatment in an argon gas at 600° C. for 1 hour as a primer treatment.The whole surface of the pieces of magnet having been subjected to theprimer treatment was spray-coated with a solvent based phenol-modifiedepoxy resin (FASTITE No. 180, produced by Ohashi Chemical Industries,Ltd.), and it was subjected to a heat treatment at 180° C. for 20minutes to form an organic insulating film having a thickness of 20 μmon the whole surface of the pieces of magnet. The pieces of magnethaving the insulating film on the whole surface thereof were subjectedto the corrosion resistance test described in Example A, and noformation of rust was observed. An integrated magnet body (l/L: 1.2%)was produced by using the pieces of magnet having the insulating film onthe whole surface thereof in the same manner as in Example A andevaluated for motor efficiency, and an IPM having the integrated magnetbody installed therein exhibited a motor efficiency of 87%.

Industrial Applicability

As described in the foregoing, because the integrated magnet bodyaccording to the invention has a film having excellent insulatingproperty only with a thin film between pieces of magnet, the eddycurrent loss and the heat generation of the magnet can be effectivelysuppressed, and the effective volume ratio of the magnet can beimproved, whereby improvement of the motor characteristics can beattained, which brings about improvement of the efficiency of the motor.Furthermore, the dimensional accuracy of the integrated magnet body canalso be improved, whereby miniaturization and high performance of themotor can be attained along with improvement of the motor efficiency.

What is claimed is:
 1. An integrated magnet body formed by laminatingand securing a plurality of pieces of magnet through an insulating filmbetween pieces of magnet, characterized in that the insulating film hasa film thickness of 0.01 μm or more, and a ratio (l/L) of a total sum ofthe thickness of the insulating films (l) to an overall length in thelaminating direction of the integrated magnet body (L) is in a range offrom 0.0005 to 3%.
 2. An integrated magnet body as claimed in the claim1, characterized in that the film thickness of the insulating film is 50μm or less.
 3. An integrated magnet body as claimed in claim 1,characterized in that the ratio (l/L) of the total sum of the thicknessof the insulating films (l) to the overall length in the laminatingdirection of the integrated magnet body (L) is in a range of from 0.01to 1%.
 4. An integrated magnet body as claimed in claim 1, characterizedin that the insulating film is an inorganic insulating film containing,as a main component, at least one selected from a chromium oxide, aphosphorous oxide, a silicon oxide, an aluminum oxide, a titanium oxideand a zirconium oxide.
 5. An integrated magnet body as claimed in claim1, characterized in that the insulating film is an organic insulatingfilm containing a thermoplastic resin and/or a thermosetting resin. 6.An integrated magnet body as claimed in claim 1, characterized in thatthe integrated magnet body is formed by scouring by encompassing andintegrating, with an organic resin, a laminated body obtained bylaminating a plurality of pieces of magnet through an insulating filmbetween the pieces of magnet.
 7. n integrated magnet body as claimed inclaim 1, characterized in that the integrated magnet body is formed bysecuring by binding, with a high strength fiber strip, a laminated bodyobtained by laminating a plurality of pieces of magnet through aninsulating film between the pieces of magnet.
 8. An integrated magnetbody as claimed in claim 1 , characterized in that the pieces of magnetare a rare earth metal-based permanent magnet.
 9. A motor characterizedby comprising an integrated magnet body as claimed in claim 1 installedtherein.